The long-range objectives center on the synthesis and testing of compounds related to ribonucleosides, deoxyribonucleosides, coenzymes, and cofactor analogues, especially those showing cell-division and cell-growth activity. We plan to develop a series of dimensional probes, purine ring analogues with known dimensional alterations, so that the limiting size of the enzyme binding region for the substrate or cofactor can be accurately defined. Related series are to be synthesized and tested for enzyme inhibition and resulting delineation of the spatial requirements for binding with exclusion of the normal substrate. We will develop along with these dimensional probes, most of which are - or are expected to be - fluorescent, fluorescent photoaffinity labels and reagents that can be used to render specific nucleic acid components fluorescent and thus to probe tRNA, viral RNA, other RNA structures, and chromosomes. Specific modifications will also be investigated which may cause chemical mutations. We will continue to synthesize and test the biological activity and binding of photoaffinity-labeled eukaryotic hormones: cytokinins for plants and 1-substituted adenines that control meiosis in starfish. The goal is to determine the receptors and the spatial and binding requirements at the specific receptor sites. The T4-induced RNA ligase enzyme will be used with fluorescent analogues of ribonucleoside 3',5'-bisphosphates to incorporate the modified nucleosides in oligomers of ordered structure for the purpose of probing inter-base interactions and interactions with the 3' terminus of tRNA's